Charged particle beam devices are used for analyzing and examining objects (hereinafter also called samples) in order to obtain insights with regard to the properties and behavior of the objects under specific conditions. One of those charged particle beam devices is an electron beam device, in particular a scanning electron microscope (also known as SEM).
In an SEM, an electron beam (hereinafter also called primary electron beam) is generated using a beam generator. The electrons of the primary electron beam are accelerated to a predeterminable energy and focused by a beam guiding system, in particular an objective lens, onto a sample to be analyzed (that is to say an object to be analyzed). A high-voltage source having a predeterminable acceleration voltage is used for acceleration purposes. Using a deflection unit, the primary electron beam is guided in a raster-type fashion over a surface of the sample to be analyzed. In this case, the electrons of the primary electron beam interact with the material of the sample to be analyzed. In particular, interaction particles and/or interaction radiation arise(s) as a consequence of the interaction. By way of example, electrons are emitted by the sample to be analyzed (so-called secondary electrons) and electrons of the primary electron beam are backscattered at the sample to be analyzed (so-called backscattered electrons). The secondary electrons and backscattered electrons are detected and used for image generation. An image of the sample to be analyzed is thus obtained.
The interaction radiation comprises X-rays and/or cathodoluminescence light and may be detected with a radiation detector. When measuring X-rays with the radiation detector, in particular energy-dispersive X-ray spectroscopy (also known as EDS or EDX) may be carried out. EDX is an analytical analysis method used for the elemental analysis or chemical characterization.
An ion beam device is also known from the prior art. The ion beam device comprises an ion beam column having an ion beam generator. Ions are generated which are used for processing a sample (for example for removing a layer of the sample or for depositing material on the sample, wherein the material is provided by a gas injection system) or else for imaging.
Furthermore, it is known from the prior art to use combination devices for processing and/or for analyzing a sample, wherein both electrons and ions can be guided onto a sample to be processed and/or to be analyzed. By way of example, it is known for an SEM to be additionally equipped with an ion beam column as mentioned above. The SEM serves, in particular, for observing the processing, but also for further analysis of the processed or non-processed sample. Electrons may also be used for depositing material. This is known as electron beam induced deposition (EBID).
EDX is often used as analytical analysis method for analyzing rocks in the field of mineralogy. It is possible to identify the composition of a mineral grain which is important information, in particular for a petrologist who needs to accurately determine the mineralogy of a rock. EDX often requires irradiating a sample with electrons of an SEM having a landing energy of at least 15 keV. The landing energy is the energy which the electrons have when impinging onto the sample. Electrons having such an energy penetrate rather deep into a sample and generate X-rays from a volume unit of the sample comprising an extension of approximately 2 μm in a first direction, in a second direction and in a third direction. Therefore, the volume unit comprises dimensions of approximately 2 μm×2 μm×2 μm. Accordingly, the volume unit also comprises a volume unit surface of 2 μm×2 μm. The volume unit surface is also called an EDX pixel.
Most mudrocks to be analyzed comprise mineral grains which are smaller than 2 μm. Therefore, they are smaller than the EDX pixel. Accordingly, an EDX spectrum which is generated based on X-rays emitted from the volume unit may comprise not only information about a single mineral grain of interest, but also about further surrounding mineral grains located in the volume unit. Therefore, the information provided by the EDX spectrum may be impossible to understand or may lead to a false result.
It is desirable to provide a method for analyzing an object using a charged particle beam device and a charged particle beam device for carrying out the method which make it possible that a petrologist may accurately determine the mineralogy of a rock.